Commit-ID: 8704baab9bc848b58c129fed6b591bb84ec02f41
Gitweb: http://git.kernel.org/tip/8704baab9bc848b58c129fed6b591bb84ec02f41
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Thu, 31 Dec 2015 18:33:22 -0800
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Thu, 31 Mar 2016 13:37:38 -0700
rcutorture: Add RCU grace-period performance tests
This commit adds a new rcuperf module that carries out simple performance
tests of RCU grace periods.
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
---
kernel/rcu/Makefile | 1 +
kernel/rcu/rcuperf.c | 637 +++++++++++++++++++++++++++++++++++++++++++++++++++
lib/Kconfig.debug | 33 +++
3 files changed, 671 insertions(+)
diff --git a/kernel/rcu/Makefile b/kernel/rcu/Makefile
index 032b2c0..18dfc48 100644
--- a/kernel/rcu/Makefile
+++ b/kernel/rcu/Makefile
@@ -5,6 +5,7 @@ KCOV_INSTRUMENT := n
obj-y += update.o sync.o
obj-$(CONFIG_SRCU) += srcu.o
obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o
+obj-$(CONFIG_RCU_PERF_TEST) += rcuperf.o
obj-$(CONFIG_TREE_RCU) += tree.o
obj-$(CONFIG_PREEMPT_RCU) += tree.o
obj-$(CONFIG_TREE_RCU_TRACE) += tree_trace.o
diff --git a/kernel/rcu/rcuperf.c b/kernel/rcu/rcuperf.c
new file mode 100644
index 0000000..9d54a57
--- /dev/null
+++ b/kernel/rcu/rcuperf.c
@@ -0,0 +1,637 @@
+/*
+ * Read-Copy Update module-based performance-test facility
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, you can access it online at
+ * http://www.gnu.org/licenses/gpl-2.0.html.
+ *
+ * Copyright (C) IBM Corporation, 2015
+ *
+ * Authors: Paul E. McKenney <paulmck@xxxxxxxxxx>
+ */
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/kthread.h>
+#include <linux/err.h>
+#include <linux/spinlock.h>
+#include <linux/smp.h>
+#include <linux/rcupdate.h>
+#include <linux/interrupt.h>
+#include <linux/sched.h>
+#include <linux/atomic.h>
+#include <linux/bitops.h>
+#include <linux/completion.h>
+#include <linux/moduleparam.h>
+#include <linux/percpu.h>
+#include <linux/notifier.h>
+#include <linux/reboot.h>
+#include <linux/freezer.h>
+#include <linux/cpu.h>
+#include <linux/delay.h>
+#include <linux/stat.h>
+#include <linux/srcu.h>
+#include <linux/slab.h>
+#include <asm/byteorder.h>
+#include <linux/torture.h>
+#include <linux/vmalloc.h>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>");
+
+#define PERF_FLAG "-perf:"
+#define PERFOUT_STRING(s) \
+ pr_alert("%s" PERF_FLAG s "\n", perf_type)
+#define VERBOSE_PERFOUT_STRING(s) \
+ do { if (verbose) pr_alert("%s" PERF_FLAG " %s\n", perf_type, s); } while (0)
+#define VERBOSE_PERFOUT_ERRSTRING(s) \
+ do { if (verbose) pr_alert("%s" PERF_FLAG "!!! %s\n", perf_type, s); } while (0)
+
+torture_param(bool, gp_exp, true, "Use expedited GP wait primitives");
+torture_param(int, nreaders, -1, "Number of RCU reader threads");
+torture_param(int, nwriters, -1, "Number of RCU updater threads");
+torture_param(bool, shutdown, false, "Shutdown at end of performance tests.");
+torture_param(bool, verbose, true, "Enable verbose debugging printk()s");
+
+static char *perf_type = "rcu";
+module_param(perf_type, charp, 0444);
+MODULE_PARM_DESC(perf_type, "Type of RCU to performance-test (rcu, rcu_bh, ...)");
+
+static int nrealreaders;
+static int nrealwriters;
+static struct task_struct **writer_tasks;
+static struct task_struct **reader_tasks;
+static struct task_struct *shutdown_task;
+
+static u64 **writer_durations;
+static int *writer_n_durations;
+static atomic_t n_rcu_perf_reader_started;
+static atomic_t n_rcu_perf_writer_started;
+static atomic_t n_rcu_perf_writer_finished;
+static wait_queue_head_t shutdown_wq;
+static u64 t_rcu_perf_writer_started;
+static u64 t_rcu_perf_writer_finished;
+static unsigned long b_rcu_perf_writer_started;
+static unsigned long b_rcu_perf_writer_finished;
+
+static int rcu_perf_writer_state;
+#define RTWS_INIT 0
+#define RTWS_EXP_SYNC 1
+#define RTWS_SYNC 2
+#define RTWS_IDLE 2
+#define RTWS_STOPPING 3
+
+#define MAX_MEAS 10000
+#define MIN_MEAS 100
+
+#if defined(MODULE) || defined(CONFIG_RCU_PERF_TEST_RUNNABLE)
+#define RCUPERF_RUNNABLE_INIT 1
+#else
+#define RCUPERF_RUNNABLE_INIT 0
+#endif
+static int perf_runnable = RCUPERF_RUNNABLE_INIT;
+module_param(perf_runnable, int, 0444);
+MODULE_PARM_DESC(perf_runnable, "Start rcuperf at boot");
+
+/*
+ * Operations vector for selecting different types of tests.
+ */
+
+struct rcu_perf_ops {
+ int ptype;
+ void (*init)(void);
+ void (*cleanup)(void);
+ int (*readlock)(void);
+ void (*readunlock)(int idx);
+ unsigned long (*started)(void);
+ unsigned long (*completed)(void);
+ unsigned long (*exp_completed)(void);
+ void (*sync)(void);
+ void (*exp_sync)(void);
+ const char *name;
+};
+
+static struct rcu_perf_ops *cur_ops;
+
+/*
+ * Definitions for rcu perf testing.
+ */
+
+static int rcu_perf_read_lock(void) __acquires(RCU)
+{
+ rcu_read_lock();
+ return 0;
+}
+
+static void rcu_perf_read_unlock(int idx) __releases(RCU)
+{
+ rcu_read_unlock();
+}
+
+static unsigned long __maybe_unused rcu_no_completed(void)
+{
+ return 0;
+}
+
+static void rcu_sync_perf_init(void)
+{
+}
+
+static struct rcu_perf_ops rcu_ops = {
+ .ptype = RCU_FLAVOR,
+ .init = rcu_sync_perf_init,
+ .readlock = rcu_perf_read_lock,
+ .readunlock = rcu_perf_read_unlock,
+ .started = rcu_batches_started,
+ .completed = rcu_batches_completed,
+ .exp_completed = rcu_exp_batches_completed,
+ .sync = synchronize_rcu,
+ .exp_sync = synchronize_rcu_expedited,
+ .name = "rcu"
+};
+
+/*
+ * Definitions for rcu_bh perf testing.
+ */
+
+static int rcu_bh_perf_read_lock(void) __acquires(RCU_BH)
+{
+ rcu_read_lock_bh();
+ return 0;
+}
+
+static void rcu_bh_perf_read_unlock(int idx) __releases(RCU_BH)
+{
+ rcu_read_unlock_bh();
+}
+
+static struct rcu_perf_ops rcu_bh_ops = {
+ .ptype = RCU_BH_FLAVOR,
+ .init = rcu_sync_perf_init,
+ .readlock = rcu_bh_perf_read_lock,
+ .readunlock = rcu_bh_perf_read_unlock,
+ .started = rcu_batches_started_bh,
+ .completed = rcu_batches_completed_bh,
+ .exp_completed = rcu_exp_batches_completed_sched,
+ .sync = synchronize_rcu_bh,
+ .exp_sync = synchronize_rcu_bh_expedited,
+ .name = "rcu_bh"
+};
+
+/*
+ * Definitions for srcu perf testing.
+ */
+
+DEFINE_STATIC_SRCU(srcu_ctl_perf);
+static struct srcu_struct *srcu_ctlp = &srcu_ctl_perf;
+
+static int srcu_perf_read_lock(void) __acquires(srcu_ctlp)
+{
+ return srcu_read_lock(srcu_ctlp);
+}
+
+static void srcu_perf_read_unlock(int idx) __releases(srcu_ctlp)
+{
+ srcu_read_unlock(srcu_ctlp, idx);
+}
+
+static unsigned long srcu_perf_completed(void)
+{
+ return srcu_batches_completed(srcu_ctlp);
+}
+
+static void srcu_perf_synchronize(void)
+{
+ synchronize_srcu(srcu_ctlp);
+}
+
+static void srcu_perf_synchronize_expedited(void)
+{
+ synchronize_srcu_expedited(srcu_ctlp);
+}
+
+static struct rcu_perf_ops srcu_ops = {
+ .ptype = SRCU_FLAVOR,
+ .init = rcu_sync_perf_init,
+ .readlock = srcu_perf_read_lock,
+ .readunlock = srcu_perf_read_unlock,
+ .started = NULL,
+ .completed = srcu_perf_completed,
+ .exp_completed = srcu_perf_completed,
+ .sync = srcu_perf_synchronize,
+ .exp_sync = srcu_perf_synchronize_expedited,
+ .name = "srcu"
+};
+
+/*
+ * Definitions for sched perf testing.
+ */
+
+static int sched_perf_read_lock(void)
+{
+ preempt_disable();
+ return 0;
+}
+
+static void sched_perf_read_unlock(int idx)
+{
+ preempt_enable();
+}
+
+static struct rcu_perf_ops sched_ops = {
+ .ptype = RCU_SCHED_FLAVOR,
+ .init = rcu_sync_perf_init,
+ .readlock = sched_perf_read_lock,
+ .readunlock = sched_perf_read_unlock,
+ .started = rcu_batches_started_sched,
+ .completed = rcu_batches_completed_sched,
+ .exp_completed = rcu_exp_batches_completed_sched,
+ .sync = synchronize_sched,
+ .exp_sync = synchronize_sched_expedited,
+ .name = "sched"
+};
+
+#ifdef CONFIG_TASKS_RCU
+
+/*
+ * Definitions for RCU-tasks perf testing.
+ */
+
+static int tasks_perf_read_lock(void)
+{
+ return 0;
+}
+
+static void tasks_perf_read_unlock(int idx)
+{
+}
+
+static struct rcu_perf_ops tasks_ops = {
+ .ptype = RCU_TASKS_FLAVOR,
+ .init = rcu_sync_perf_init,
+ .readlock = tasks_perf_read_lock,
+ .readunlock = tasks_perf_read_unlock,
+ .started = rcu_no_completed,
+ .completed = rcu_no_completed,
+ .sync = synchronize_rcu_tasks,
+ .exp_sync = synchronize_rcu_tasks,
+ .name = "tasks"
+};
+
+#define RCUPERF_TASKS_OPS &tasks_ops,
+
+static bool __maybe_unused torturing_tasks(void)
+{
+ return cur_ops == &tasks_ops;
+}
+
+#else /* #ifdef CONFIG_TASKS_RCU */
+
+#define RCUPERF_TASKS_OPS
+
+static bool __maybe_unused torturing_tasks(void)
+{
+ return false;
+}
+
+#endif /* #else #ifdef CONFIG_TASKS_RCU */
+
+/*
+ * If performance tests complete, wait for shutdown to commence.
+ */
+static void rcu_perf_wait_shutdown(void)
+{
+ cond_resched_rcu_qs();
+ if (atomic_read(&n_rcu_perf_writer_finished) < nrealwriters)
+ return;
+ while (!torture_must_stop())
+ schedule_timeout_uninterruptible(1);
+}
+
+/*
+ * RCU perf reader kthread. Repeatedly does empty RCU read-side
+ * critical section, minimizing update-side interference.
+ */
+static int
+rcu_perf_reader(void *arg)
+{
+ unsigned long flags;
+ int idx;
+
+ VERBOSE_PERFOUT_STRING("rcu_perf_reader task started");
+ set_user_nice(current, MAX_NICE);
+ atomic_inc(&n_rcu_perf_reader_started);
+
+ do {
+ local_irq_save(flags);
+ idx = cur_ops->readlock();
+ cur_ops->readunlock(idx);
+ local_irq_restore(flags);
+ rcu_perf_wait_shutdown();
+ } while (!torture_must_stop());
+ torture_kthread_stopping("rcu_perf_reader");
+ return 0;
+}
+
+/*
+ * RCU perf writer kthread. Repeatedly does a grace period.
+ */
+static int
+rcu_perf_writer(void *arg)
+{
+ int i = 0;
+ int i_max;
+ long me = (long)arg;
+ bool started = false, done = false, alldone = false;
+ u64 t;
+ u64 *wdp;
+ u64 *wdpp = writer_durations[me];
+
+ VERBOSE_PERFOUT_STRING("rcu_perf_writer task started");
+ WARN_ON(rcu_gp_is_expedited() && !rcu_gp_is_normal() && !gp_exp);
+ WARN_ON(rcu_gp_is_normal() && gp_exp);
+ WARN_ON(!wdpp);
+ t = ktime_get_mono_fast_ns();
+ if (atomic_inc_return(&n_rcu_perf_writer_started) >= nrealwriters) {
+ t_rcu_perf_writer_started = t;
+ if (gp_exp) {
+ b_rcu_perf_writer_started =
+ cur_ops->exp_completed() / 2;
+ } else {
+ b_rcu_perf_writer_started =
+ cur_ops->completed();
+ }
+ }
+
+ do {
+ wdp = &wdpp[i];
+ *wdp = ktime_get_mono_fast_ns();
+ if (gp_exp) {
+ rcu_perf_writer_state = RTWS_EXP_SYNC;
+ cur_ops->exp_sync();
+ } else {
+ rcu_perf_writer_state = RTWS_SYNC;
+ cur_ops->sync();
+ }
+ rcu_perf_writer_state = RTWS_IDLE;
+ t = ktime_get_mono_fast_ns();
+ *wdp = t - *wdp;
+ i_max = i;
+ if (!started &&
+ atomic_read(&n_rcu_perf_writer_started) >= nrealwriters)
+ started = true;
+ if (!done && i >= MIN_MEAS) {
+ done = true;
+ pr_alert("%s" PERF_FLAG
+ "rcu_perf_writer %ld has %d measurements\n",
+ perf_type, me, MIN_MEAS);
+ if (atomic_inc_return(&n_rcu_perf_writer_finished) >=
+ nrealwriters) {
+ PERFOUT_STRING("Test complete");
+ t_rcu_perf_writer_finished = t;
+ if (gp_exp) {
+ b_rcu_perf_writer_finished =
+ cur_ops->exp_completed() / 2;
+ } else {
+ b_rcu_perf_writer_finished =
+ cur_ops->completed();
+ }
+ smp_mb(); /* Assign before wake. */
+ wake_up(&shutdown_wq);
+ }
+ }
+ if (done && !alldone &&
+ atomic_read(&n_rcu_perf_writer_finished) >= nrealwriters)
+ alldone = true;
+ if (started && !alldone && i < MAX_MEAS - 1)
+ i++;
+ rcu_perf_wait_shutdown();
+ } while (!torture_must_stop());
+ rcu_perf_writer_state = RTWS_STOPPING;
+ writer_n_durations[me] = i_max;
+ torture_kthread_stopping("rcu_perf_writer");
+ return 0;
+}
+
+static inline void
+rcu_perf_print_module_parms(struct rcu_perf_ops *cur_ops, const char *tag)
+{
+ pr_alert("%s" PERF_FLAG
+ "--- %s: nreaders=%d nwriters=%d verbose=%d shutdown=%d\n",
+ perf_type, tag, nrealreaders, nrealwriters, verbose, shutdown);
+}
+
+static void
+rcu_perf_cleanup(void)
+{
+ int i;
+ int j;
+ int ngps = 0;
+ u64 *wdp;
+ u64 *wdpp;
+
+ if (torture_cleanup_begin())
+ return;
+
+ if (reader_tasks) {
+ for (i = 0; i < nrealreaders; i++)
+ torture_stop_kthread(rcu_perf_reader,
+ reader_tasks[i]);
+ kfree(reader_tasks);
+ }
+
+ if (writer_tasks) {
+ for (i = 0; i < nrealwriters; i++) {
+ torture_stop_kthread(rcu_perf_writer,
+ writer_tasks[i]);
+ if (!writer_n_durations)
+ continue;
+ j = writer_n_durations[i];
+ pr_alert("%s%s writer %d gps: %d\n",
+ perf_type, PERF_FLAG, i, j);
+ ngps += j;
+ }
+ pr_alert("%s%s start: %llu end: %llu duration: %llu gps: %d batches: %ld\n",
+ perf_type, PERF_FLAG,
+ t_rcu_perf_writer_started, t_rcu_perf_writer_finished,
+ t_rcu_perf_writer_finished -
+ t_rcu_perf_writer_started,
+ ngps,
+ b_rcu_perf_writer_finished -
+ b_rcu_perf_writer_started);
+ for (i = 0; i < nrealwriters; i++) {
+ if (!writer_durations)
+ break;
+ if (!writer_n_durations)
+ continue;
+ wdpp = writer_durations[i];
+ if (!wdpp)
+ continue;
+ for (j = 0; j <= writer_n_durations[i]; j++) {
+ wdp = &wdpp[j];
+ pr_alert("%s%s %4d writer-duration: %5d %llu\n",
+ perf_type, PERF_FLAG,
+ i, j, *wdp);
+ if (j % 100 == 0)
+ schedule_timeout_uninterruptible(1);
+ }
+ kfree(writer_durations[i]);
+ }
+ kfree(writer_tasks);
+ kfree(writer_durations);
+ kfree(writer_n_durations);
+ }
+
+ /* Do flavor-specific cleanup operations. */
+ if (cur_ops->cleanup != NULL)
+ cur_ops->cleanup();
+
+ torture_cleanup_end();
+}
+
+/*
+ * Return the number if non-negative. If -1, the number of CPUs.
+ * If less than -1, that much less than the number of CPUs, but
+ * at least one.
+ */
+static int compute_real(int n)
+{
+ int nr;
+
+ if (n >= 0) {
+ nr = n;
+ } else {
+ nr = num_online_cpus() + 1 + n;
+ if (nr <= 0)
+ nr = 1;
+ }
+ return nr;
+}
+
+/*
+ * RCU perf shutdown kthread. Just waits to be awakened, then shuts
+ * down system.
+ */
+static int
+rcu_perf_shutdown(void *arg)
+{
+ do {
+ wait_event(shutdown_wq,
+ atomic_read(&n_rcu_perf_writer_finished) >=
+ nrealwriters);
+ } while (atomic_read(&n_rcu_perf_writer_finished) < nrealwriters);
+ smp_mb(); /* Wake before output. */
+ rcu_perf_cleanup();
+ kernel_power_off();
+ return -EINVAL;
+}
+
+static int __init
+rcu_perf_init(void)
+{
+ long i;
+ int firsterr = 0;
+ static struct rcu_perf_ops *perf_ops[] = {
+ &rcu_ops, &rcu_bh_ops, &srcu_ops, &sched_ops,
+ RCUPERF_TASKS_OPS
+ };
+
+ if (!torture_init_begin(perf_type, verbose, &perf_runnable))
+ return -EBUSY;
+
+ /* Process args and tell the world that the perf'er is on the job. */
+ for (i = 0; i < ARRAY_SIZE(perf_ops); i++) {
+ cur_ops = perf_ops[i];
+ if (strcmp(perf_type, cur_ops->name) == 0)
+ break;
+ }
+ if (i == ARRAY_SIZE(perf_ops)) {
+ pr_alert("rcu-perf: invalid perf type: \"%s\"\n",
+ perf_type);
+ pr_alert("rcu-perf types:");
+ for (i = 0; i < ARRAY_SIZE(perf_ops); i++)
+ pr_alert(" %s", perf_ops[i]->name);
+ pr_alert("\n");
+ firsterr = -EINVAL;
+ goto unwind;
+ }
+ if (cur_ops->init)
+ cur_ops->init();
+
+ nrealwriters = compute_real(nwriters);
+ nrealreaders = compute_real(nreaders);
+ atomic_set(&n_rcu_perf_reader_started, 0);
+ atomic_set(&n_rcu_perf_writer_started, 0);
+ atomic_set(&n_rcu_perf_writer_finished, 0);
+ rcu_perf_print_module_parms(cur_ops, "Start of test");
+
+ /* Start up the kthreads. */
+
+ if (shutdown) {
+ init_waitqueue_head(&shutdown_wq);
+ firsterr = torture_create_kthread(rcu_perf_shutdown, NULL,
+ shutdown_task);
+ if (firsterr)
+ goto unwind;
+ schedule_timeout_uninterruptible(1);
+ }
+ reader_tasks = kcalloc(nrealreaders, sizeof(reader_tasks[0]),
+ GFP_KERNEL);
+ if (reader_tasks == NULL) {
+ VERBOSE_PERFOUT_ERRSTRING("out of memory");
+ firsterr = -ENOMEM;
+ goto unwind;
+ }
+ for (i = 0; i < nrealreaders; i++) {
+ firsterr = torture_create_kthread(rcu_perf_reader, NULL,
+ reader_tasks[i]);
+ if (firsterr)
+ goto unwind;
+ }
+ while (atomic_read(&n_rcu_perf_reader_started) < nrealreaders)
+ schedule_timeout_uninterruptible(1);
+ writer_tasks = kcalloc(nrealwriters, sizeof(reader_tasks[0]),
+ GFP_KERNEL);
+ writer_durations = kcalloc(nrealwriters, sizeof(*writer_durations),
+ GFP_KERNEL);
+ writer_n_durations =
+ kcalloc(nrealwriters, sizeof(*writer_n_durations),
+ GFP_KERNEL);
+ if (!writer_tasks || !writer_durations || !writer_n_durations) {
+ VERBOSE_PERFOUT_ERRSTRING("out of memory");
+ firsterr = -ENOMEM;
+ goto unwind;
+ }
+ for (i = 0; i < nrealwriters; i++) {
+ writer_durations[i] =
+ kcalloc(MAX_MEAS, sizeof(*writer_durations[i]),
+ GFP_KERNEL);
+ if (!writer_durations[i])
+ goto unwind;
+ firsterr = torture_create_kthread(rcu_perf_writer, (void *)i,
+ writer_tasks[i]);
+ if (firsterr)
+ goto unwind;
+ }
+ torture_init_end();
+ return 0;
+
+unwind:
+ torture_init_end();
+ rcu_perf_cleanup();
+ return firsterr;
+}
+
+module_init(rcu_perf_init);
+module_exit(rcu_perf_cleanup);
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 1e9a607..f4b797a 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1289,6 +1289,39 @@ config TORTURE_TEST
tristate
default n
+config RCU_PERF_TEST
+ tristate "performance tests for RCU"
+ depends on DEBUG_KERNEL
+ select TORTURE_TEST
+ select SRCU
+ select TASKS_RCU
+ default n
+ help
+ This option provides a kernel module that runs performance
+ tests on the RCU infrastructure. The kernel module may be built
+ after the fact on the running kernel to be tested, if desired.
+
+ Say Y here if you want RCU performance tests to be built into
+ the kernel.
+ Say M if you want the RCU performance tests to build as a module.
+ Say N if you are unsure.
+
+config RCU_PERF_TEST_RUNNABLE
+ bool "performance tests for RCU runnable by default"
+ depends on RCU_PERF_TEST = y
+ default n
+ help
+ This option provides a way to build the RCU performance tests
+ directly into the kernel without them starting up at boot time.
+ You can use /sys/module to manually override this setting.
+ This /proc file is available only when the RCU performance
+ tests have been built into the kernel.
+
+ Say Y here if you want the RCU performance tests to start during
+ boot (you probably don't).
+ Say N here if you want the RCU performance tests to start only
+ after being manually enabled via /sys/module.
+
config RCU_TORTURE_TEST
tristate "torture tests for RCU"
depends on DEBUG_KERNEL
--
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